1. Field of the Invention
The present invention relates to an electrical actuator for forming the shed in a weaving loom, particularly for controlling the harness cords of a weaving system of the Jacquard type or the frames of a dobby, and to a process for manufacturing such an actuator. The invention also relates to a weaving system comprising such an actuator, and to a weaving loom equipped with such a system.
2. Brief Description of the Related Art
In weaving systems of the Jacquard type, it is known to drive, in phase opposition, two frames each bearing a plurality of griffes or horizontal knives adapted to displace, vertically, hooks connected to the harness cords by a pulley or block mechanism. Mechanical or electro-mechanical devices are provided to immobilize these hooks along their vertical stroke. This known type of device necessitates considerable power for moving the griffe frames, which power is furnished by the drive shaft of the weaving loom, this leading to said loom being overdimensioned.
It is also known to use a rotating motor such as a step motor or a servo-motor to control a small cord belonging to a weaving loom, linearly. Taking into account the large number of electric motors used in the weaving system associated with a weaving loom, a number which may attain and even exceed 10,000, these motors must be of minimum space requirement and cost, while having considerable reliability. In particular, winding of the conducting wire must effected rapidly while guaranteeing a sufficient level of quality. In addition, the stator must have dimensions adapted to those of the rotor which, in order to optimize its inertia, must have a diameter which is as small as possible. Finally, the manufacturing tolerances of the metal plates constituting the stacks forming the stators must not hinder manufacture thereof nor reduce their yield.
It Is an object of the present invention to propose an electrical rotating actuator adapted to control displacement of one or more harness cords, which is compact and simple to manufacture.
To that end, the invention relates to an electrical actuator for forming the shed in a weaving loom, particularly for controlling the harness cords of a weaving system of the Jacquard type or the frames of a dobby, comprising a rotor and at least one stator whose armature is formed by a stack of metal plates, characterized in that the stator is formed by at least two stator elements disposed side by side along the axis of rotation of the rotor, each stator element comprising two zones for reception of a winding of electrically conductive wire, at least certain of the metal plates of each zone disposed opposite one another being mated.
Thanks to the invention, it is possible to produce an electrical rotating actuator in which the electromagnetic flux circulating in the stator is optimum whatever the manufacturing tolerances of the plates constituting it and, in particular, whatever the variations in thickness existing in a batch of plates. In effect, the fact that the plates are mated, in the two zones of reception of the conducting wire winding, allows an efficient transfer of the electromagnetic flux from one zone towards the other.
According to a first advantageous aspect of the invention, the mated plates in each zone are formed from a single plate extending over the whole length of the armature. Thanks to this aspect of the invention, if one plate is thicker or thinner than its neighbors variation in thickness is found over the whole length of the armature and consequently in the two zones of reception of the electric wire winding. There is therefore no defect in alignment of the plates constituting the armatures, this promoting the electromagnetic flux.
According to another advantageous aspect of the invention, the plates comprise, in their central part and before the armature is shaped., a cleavable bridge connecting parts intended to be partially surrounded by said electrically conducting wire winding. Thanks to this aspect of the invention, the actuater is easy to manufacture and therefore of relatively low cost, insofar as the winding of the stator can be made flat, therefore at high speed, before the final geometry of the stator is attained by rupture of the cleavable bridge.
According to another advantageous aspect of the invention, each plate extends, in a direction substantially perpendicular to the cleavable bridge, by a finger, a finger of one plate extending from one side of the bridge that it comprises, while the fingers of the two adjacent plates extend, in the same direction, on the other side of bridges that they comprise,. This construction of the cores or armatures of the stators allows a shaping of the stator, in order to produce the air gap, by wedging the fingers formed in the plates with respect to one another.
In that case, the fingers of the plates may be provided to be adapted to imbricate in one another, after rupture of the cleavable bridges. Such imbrication of the fingers of the plates forming the armatures of the stators allows a good electromagnetic contact therebetween and consequently a maximum conduction of the electromagnetic flux in the corresponding air gap.
The plates forming the stator elements are advantageously disposed head-to-tail. Thanks to this aspect of the invention, the distribution of the fingers on either side of the cleavable bridges may be obtained with one sole plate geometry, which greatly simplifies manufacture.
According to another advantageous aspect of the invention, the actuator comprises a base provided with two housings each adapted to receive a part of a stator, this base being provided with means for connecting each stator with pins for electrical supply of the actuator. This base serves as bearing structure for the actuator according to the invention.
The invention also relates to a process for manufacturing an actuator as described hereinbefore and, more specifically, to a process characterized in that it consists in producing each stator element of the actuator by winding flat on an armature and in bending the latter in order to bring the ends closer together, a housing for reception of a rotor being formed by bringing these ends closer. Flat winding of the armatures may be effected at very high speed, possibly on a plurality of armatures disposed in parallel, this enabling the manufacturing costs to be minimized.
According to a first advantageous aspect of the process according to the invention, bending of the armature is effected by rupture of cleavable bridges. The presence of the cleavable bridges guarantees a precise positioning of the different parts constituting the armature up to the instant of rupture of these bridges.
In that case, it may, in addition, be provided that bending of the armature results in the imbrication of fingers distributed alternately on either side of the cleavable bridges.
According to another advantageous aspect of the process according to the invention, it includes a step of overmolding of each stator of the actuator on a base provided with means for electrical supply of the stator or stators. The base defines the relative positioning of the stators before overmoulding thereof, while allowing their electrical supply. This base therefore makes it possible to obtain an overmolded actuator, therefore of low cost in large quantities, while guaranteeing a satisfactory level of reliability.
The invention also relates to a weaving system which comprises one or more of the actuators as described hereinabove or manufactured as indicated hereinabove, and to a weaving loom equipped with such a system. This system is easier to employ and maintain than the prior art devices, and allows a yarn-to-yarn control of a Jacquard loom harness. The yield of a weaving loom according to the invention is therefore substantially improved with respect to the known art.